Sorry for not jumping in on this but there is information missing from the question and I don't want to either mislead or give wrong info on a partitioning question.

First, it is my understanding that any upgrade to Windows 10 must be installed as an upgrade to the existing version first for Windows 10 to be properly registered for your computer. Anyone please correct me (or add info) if I am wrong about that.

Second. Under normal circumstances (I.E. using the entire disk with Windows 10 as the only OS) you would allow the Windows install program to "do it's thing". However things like existing multiple partitions or a Dell service partition you want to keep, etc, would change that.